Fire alarm switch



July 23, 1940. J. H. DERBY 2,209,193

FIRE ALARM SWITCH E ww .in 9 qu? q- ...LLV-L" ATTORNEYS July 23, 1940. J. H. DERBY FIRE ALARM SWITCH Filed Aug. 5, 1957 2 Sheets-Sheet 2 Patented `luly 23, 1940 UNITED STATES @ATENT OFFICE 4 Claims.

This invention relates to thermostatic circuit controlling devices of the types which are particularly adapted for use in fire alarm or re control systems.

5 Thermostatic circuit controlling devices for the aforementioned purposes are of two general types: Those operating upon a rise of temperature above a predetermined maximum and those operating when the temperature rises at a cer- V tain rate, the latter type being commonly referred to as rate-of-rise thermostats. Some advantages attach to the use oi each of these two types of thermostatic circuit controlling devices, depending upon the place of use. For example,

rate-of-rise systems, if not combined with some means for insuring their operation when the temperature reaches a predetermined maximum, do not always detect dangerous increases'in temperature, if these increases have been slow or gradual. Furthermore, these systems sometimes give false alarms for sudden' increases in temperature which are not associated with dangerous conditions; for example, an up-draft ofhot air resulting from the removal of thek cover from a kettle of boiling water or the opening of a door between two rooms of markedly different temperatures.

Ideal protection, therefore, usually demands the combination of thermostatic means operating on the rate-of-rise principle with thermostatic means operating when the temperature exceeds a predetermined maximum so that both the quick rise in temperature which is dangerous can be detected and also the more slow but often equally dangerous rise in temperature beyond a predetermined maximum.

An object of the present invention, therefore, is to provide thermostatic circuit controlling means operable both by sudden increases in the o temperature of the space protected thereby and also by the rise of the temperature beyond a predetermined safe maximum.

Many thermostatic circuit controlling systems, both those that operate on the rate-oi-rise principle and those that operate when the temperature rises above a predetermined maximum are constructed so that they are automatically reset. There are some advantages in this, in that the system is always ready to operate.

But automatic resetting also has its disadvantages, particularly where there is no intermediate mechanically or electrically driven signal transmitting means set in operation by the thermostat. If, for example, a re starts where there is a rate-of-rise system Without the intermediate,

(Cl. 20G-140) independently operated signal transmitting means and the fire smolders without further increase in the room temperature, then the system, after giving an initial alarm, may adjust itself to the constant temperature and cease to give an alarm, leading a distant attendant to believe that there was no re or that it has been extinguished. Likewise with thermostatic controlling devices operating on the principle of a rise of the temperature above a predetermined 1o maximum, in the absence of intermediate, independently driven signal transmitting means, the falling of the temperature in the neighborhood of the thermostat may not necessarily indicate that the re has been completely taken 15 care of and yet the thermostat may reset itself and thus fail to continue to give an alarm. It is therefore frequently advisable to provide that the thermostatically actuated circuit controlling means, when operated, remain in operative alarm-sending condition until an inspection of the place from which the alarm was sent has been made.

One of the objects of the present invention is to provid-e `for the maintenance o the operative 25 circuit to the alarm or other signal system, when completed by the action of the thermostat, until the attendant effects the resetting of the controlling means, thus placing upon him the responsibility for having done something to insure him- 30 self that there is no further occasion for alarm. At the same time the invention provides for the simple and convenient resetting of the thermostatic circuit controlling means into condition for operation again when the occasion demands. 3-

An important feature of the invention is the utilization of means operating independently of the thermostatic elements but arranged to be actuated thereby for effecting the circuit changing movements of the circuit controlling mechanism whereby reliance upon either the making or maintenance of circuit establishing contacts by the thermostatic elements or by parts moving therewith is unnecessary.

Another important feature of the invention is the arrangement of the parts of the thermostatically actuated circuit controlling mechanism so that they can readily be automatically supervised.

Other objects and important features of the invention will appear from the following description and claims when considered in connection with the accompanying drawings in which a thermostatically actuated circuit controlling device embodying the present invention is illustrated in a preferred embodiment, the drawings for con- 55 venience showing this device in inverted position, that is, with the dome at the top whereas when in use on the ceiling of a room to be protected thereby the dome will extend downward.

In the drawings-y Figure l is a vertical section through thermostatically actuated circuit controlling means embodying the present invention, the device illustrated .in the drawings being shown in inverted position and the section being taken approximately on the line I-l of Figure 3 but with the dome and all of the other elements of the device in position except that a part of the dome is shown as broken away;

Figure 2 is a sectional detail illustrating the metering vent connected with the air chamber in the dome and also the test vent;

Figure 3 is a plan view ofthe apparatus but with the dome, associated diaphragm and thermostatic elements removed;

Figure 4 is a vertical section on the line 4 4 of Figure 3 with the dome, associated diaphragm and thermostatic elements connected therewith, the'parts being in position for resetting after operation; l

Figure 5 is a vertical section on the line 5 5 of Figure 3 with the dome, associated diaphragm and thermostatic elements connected thereto, this View showing the diaphragm in its latched tripping position; l

Figure 6 is a vertical section on the line G- of Figure 3 with the dome, associated diaphragm and thermostatic elements in position;

Figure 'Tis a plan view 'ofl the rigid and exible diaphragms looking from the side opposite the dome.

In the illustrative embodiment of the invention those parts which might vbe'aifected by dust, corrosion, etc., are enclosed within a molded housing 2, of Bakelite or other suitable material, provided with bayonet lock recesses 4 for receiving the cooperating elementsG of bayonet joints, the elements G being carried by an outlet box 8 having on opposite sides nipples l0 provided with any suitable locking means Yl2 for the cables carrying the transmission Wires `for Athe alarm and supervisory circuits. A flanged threaded ring i4, adapted to be screwed upon a threaded portion of the housing or casing 2 of,v reduced diameter, provides a shoulder IE which serves to clamp the rolled over flange i8 of the dome 20 between said shoulder and the end ofv the housing. The ring i4 may beof brass or other suitable material. V

The dome 20, which is preferably formed of some good heat conducting, not readily corrodible material such as copper, formswith the rigid diaphragm 22 an air chamber for the rate-ofrise thermostat, this ,air Achamber having a central vent 24 through the diaphragm 22 into a" smaller air chamber formed between a flexible corrugated diaphragm 2 6 and the rigid `dia.- phragm 22, the ilexible diaphragm 23 being provided at its center with a thickened relatively rigid disk 28 serving as a bearing member for a bearing pin 30 carried bya latch lmember' 32, through which the spring-operated circuit closer is held in open position. To insure tightness of the housing 2 against dust, moisture', etc., a

gasket 34 may be provided between the ring htV and the housing. l

VExpansion of the air in the chamber formed between the dome 20 rand the rigid diaphragm 22, which are preferably lboth-made of copper or bronze for heat conducting efcienoy, will force" a portion of the air through the central vent 24 of this chamber and cause the iiexible diaphragm 26 to move its bearing member 28 away from the rigid diaphragm 22, thus causing the latch member 32 to rock about its fulcrum 36.

Also attached to the rigid diaphragm 22 at 38 is a bimetallic thermostat 4D having its free end arranged to bear against a second bearing pin 42 also carried by the latch member 32. It will be noted that both the bearing pin v3l] and the bearing pin v42 are threaded through the latch member- 32 for adjustment with respect to the yrespective thermostats and are provided with lock nuts for holding them in adjusted position.

To control the action of the rate-of-rise ther- `mostat, a slow leak is provided between the air chamber within the dome and the interior of the housing 2 so that gradual increases of the temperatureof the air in the chamber formed between the dome 2D and the rigid diaphragm 22 will drive the excess air out through this leak and thus equalize the pressure on both sides of the flexible diaphragm 26 so that the diaphragm 26 will not be moved away from the rigid diaphragm 22 for gradual temperature changes.

It has been found that a metering vent permitting a'suitable rate of discharge of the air and intake of air as the temperature varies can be constructed in the following manner:

A nipple 44, having a reduced threaded upper end adapted to be Screwed into an opening through the rigid diaphragm ZZ-and to receive a nut 46 for clamping the nipple in position, is provided with a central passage 48 which is enlarged to receive material 50 servingy as means for determining the rate of flow of the air. A suitable material for this purpose has been found to be chemically pure lambs wool. The lambs wool 50 is preferably clamped between the bottom of the enlarged portion of the passage 48 and a disk 52 having a central opening of the desired size, a threaded bushing 54 serving to press the disk 52 against the wool 50 with the desiredpressure. Y

To test the rate of flow of the air through'the passage 50 there is preferably also connected to the rigid diaphragm 2.2 a second nipple or tube 5B which may extend through the diaphragm and be provided witha lock nut 58. The tube or nipple'56 provides for the connection of any suit-l able test apparatus with the interior of the chamber between the dome 20 and the diaphragm 22 to insure proper adjustment Aof the rate-of-rise defining vent; made the -test tube or nipple 56 will be closed by means of a threaded plug E@ which is then sealed in its closed position to insure air tightness and to prevent tampering therewith.

There are preferably provided in this apparatus two circuit closers, one rfor eiecting the closing of the circuit to the central station and the other for effecting the closing of a local circuit;

When, for example, the thermostatically actuated circuit controlling device is to be used for in-v dicating res or dangerous heat conditions in the cabins of a ship, one` of the circuit closers may beused to close the circuit'to the central station where the alarm is located, and the other may be` used to close a circuit to a light near the cabin or group of cabins where the nre is located so that when the one who is to inspect tinguish the re comes tothe main corridor in Which the cabin or group of cabins is located he,

will at once be advised as to where the cabin or After the desired test has been" Cai group of cabins is located-which hasvbeen responsible for the alarm Aat the central station.

As in most iire alarm systems, it is also important that the various circuits be supervised so that there will be warning at the central station of any broken circuit. Provision is made, therefore, for such connections to the apparatus as will insure proper automatic supervision. A description of the alarm circuit closers or switches necessarily involves also a description of the switches controlling the supervisory circuits.

As hereinabove suggested in order to insure certain and positive operation the invention provides for converting the relatively small movements of the thermostats employed in the present device into positive and forceful circuit closing actions which, so far as the actual circuit effecting contacts are concerned, will be independent of the action of the actuating thermostat after the initial actuation. As herein shown, provision has been made for effecting the closing of the circuits by the release of the stored up force of a spring and also for the maintenance 'of the circuit closers in their circuit closing position until separate means, under control of the central station, has been actuated to reset the apparatus;

In the illustrative embodiment of the invention, a spring 62, bearing against the under side of one arm 54 of a bellcrank lever and put under tension by said lever when it is in its latched open circuit position shown in Figure 1, provides the stored up power for effecting the circuit closing operation of the two alarm circuit controlling switches provided in the device. The amount of tension in the spring 62 when the parts are in the position shown in Figure 1 may be varied by means of an adjusting screw 66, bearing against the under side of the spring 62.

The arm 64 of the bellcrank lever is connected to two switch members 68 and 10 in such manner that when said bellcrank arm 64 is in the position shown in Figure 1 the resilient switch members 68 and 'l0 are in position to maintain contact with the lower resilient switch members |2 and 14, respectively, in supervisory circuits. When the bellcrank arm 64 is moved by the spring 62 into the position shown in Figure 5, the switch arms 68 and 'l0 are then brought into contact with the upper resilient switch members 16 and 1B, respectively, of the cabin light circuit and of the central station alarm circuit. The switch members 68 and 1|! are insulated from the bellcrank arm 54 and from each other by Bakelite insulators and 82.

Each of the switch arms 58, 1U, 12, 14, 16 and 'i8 is formed of an elongated strip of spring metal such as phosphorbronze, with a suitable contact knob as shown, and is put under tension in both circuit closing positions so as to insure constant pressure at the contacts in either of the positions, that is, either in the position shown in Figure l, where the switches are maintaining the supervisory circuits, or in the position in Figure 5, where the switches are in their alarm circuit energizing position.

'Ihe means for maintaining the supervisory circuit switches in their supervisory circuit closing position, while at the same time maintaining the cabin light and central station alarm switches in their open circuit positions, comprises latch mechanism of which the latch member 32 hereinabove referred to is an element. As shown in the plan View of Figure 3, the arm B4 of the bellcrank lever, which is fulcrumed on a pin or shaft 86 extending between two ears or lugs 88 and 90 formed on or connected to the Bakelite base 92, is of U-form and a part thereof extends to one side of the bank of switch members 58, lil, l2, M, 'E6 and 18. The part of said U the most remote from the arm 615 carries an upright portion extending through a slot 9S in the latch member 32 and having a tooth-like formation 98 at its upper end which constitutes the catch for the latch member 32.

As will be seen, the bearing surface of the upright portion $4 of the arm which engages the end of the slot 96 in the latch member 32 is conned to the tooth-like end 98 of said upright portion 94 and therefore only a comparatively slight movement of said latch 32 upward is required to release the bellcrank and permit the action of the spring 62 to rock it about its axis from the position shown in Figure l to the position shown in Figure 5. It will be noted that the tooth-like part of the upright :3l-i is also cut back sharply from its pointed end to provide clearance for the rocking movement of the bellcrank.

To provide for the resetting of the switches and of the latch mechanism which holds them in their reset position, when they have been moved by the spring @2 into their cabin light and alarm circuit energizing positions, means is provided for rocking the bellcrank 64, 8 against the tension of the spring 52 into position to permit the latch member 32 to drop back into latching relation to the upright S4 of the bellcrank. The illustrative means for this purpose comprises an electromagnet |00, mounted at one side of the chamber in the housing 2. The magnet |643, when energized, is arranged to act on an armature |82 fulcrumed at |64 and connected by a link |06 with an upright extension |08 on the bellcrank arm 64 in such manner that when the magnet |00 is energized and pulls the armature |52 toward it the link Hit, connected to the upright extension |98 of the bellcrank 64, will rock said bellcrank into the position shown in Figure 1 and permit the latch member 32 to drop into latching relation to the upright arm 94 of the bellcrank, thus resetting the switches into the position shown in Figure l. Deenergization of the magnet |60, after the resetting operation, leaves the armature |82 free to follow the movements of the bellcrank E4 when the latch member 32 is rocked into its unlatching position.

It will be noted that the metering vent establishes communication between the chamber within the dome 2li, which has no other discharge opening, and the chamber in the housing or casing 2, which may or may not have another discharge opening, depending on whether or not it is desirable that it be absolutely air tight. It will be obvious, of course, that the apparatus will operate under either condition, the housing 2 being formed of Bakelite, a relatively poor heat conductor, whereas the dome 26 is formed of copper, a good heat conductor. Thus, while the pressures within the two chambers will be equalized by slow rates of rise of temperature owing to the leakage permitted through the metering vent, when there is a sudden rise of temperature more rapid heating of the air within the chamber in the dome will cause the flexible diaphragm 2E to move the latch member 32 into its switch tripping position.

What I claim as new is:

1. A thermostatically actuated circuit controlling unit comprising, in combination, a cylindrical casing having a removable cover and having therein a circuit closer normally impelled toward circuit closing position, a latch for holding said circuit closer in open position, the cover for said casing including a dome, a circular supporting base and a flexible diaphragm together constituting an air chamber, the plane side of said dome being coextensive with the opening to be closed and serving with said base to form a dust tight closure for said casing, said flexible diaphragm being arranged to move said latch into circuit closer releasing position when itself moved by the expansion of the air in said air chamber, and a metering vent through said base into said casing for preventing diaphragm operating expansion of the air chamber air for rates of rise of temperature below a critical rate.

2. A thermostatically actuated circuit controlling unit comprising a housing including a dome formed of heat conductingA material and adapted to be exposed to temperature changes in the room to be protected, means including a exible diaphragm for dividing the interior of said housing into two compartments, a trip switch in the compartment remote from the dome and arranged to be tripped by movement of said iiexible diaphragm brought about by expansion of the air in the dome compartment and a metering vent between the two compartments for equalizing the pressure therein when the air expands at less'than a critical rate.

3. Thermostatically actuated circuit controlling means comprising, in combination, a circuit closer normally impelled toward circuit closing position, a latch for holding said circuit closer in open positiongand a `thermostat comprising a movable element so arranged that when it is moved under the appropriate heat conditions it will eiect the movement of said latch into circuit closer releasing position, said circuit closer comprising a pair of movable switch members connected to .move together, two stationary switch members associated with each movable switch member, whereby each movable switch member may be moved from a position in which it maintains one circuit in closed condition to a position in which it closes another circuit, said latch normally holding said movable switch members in engagement with one pair of said stationary switch members and a spring acting when said latch is released to move said movable switch members into engagement with the other pair of stationary switch members.

4. A thermostatically actuated circuit controlling unit comprising a housing having therein two chambers, one provided with exposed walls of good heat conducting material and the other having its principal walls formed of poor heat conducting material, the separating wall between the two chambers comprising a exible diaphragm, a trip switch in the compartment partly enclosed by the walls of poor heat conducting material, arranged to be tripped by movement of said flexible diaphragm brought about by expansion of the air in the other compartment, and a metering vent between the two compartments for equalizing the pressure therein when the air expands at less than a critical rate.

JOHN vH. DERBY. 

